Ejector devices of this type comprise one or more ejectors containing one or more jets or nozzles arranged in sequence and through which an air flow is fed at high pressure. The compressed air is fed to the ejector via a compressed-air duct connected to a source of compressed air. The ejector is in flow communication with a space from where air is evacuated by suction into the flow of compressed air through the ejector via slits formed between the nozzles, or at the outlet of the individual jet. The evacuated space is, via an air suction duct, in flow communication with a gripping member, such as a suction cup.
The flow of compressed air to the ejector may be adjustable by means of a valve arranged in the compressed-air duct and adapted to open and shut off the flow of compressed air, and, where appropriate, for partial restriction of the flow to the ejector. The valve may be associated with an electrical control member that regulates the flow of compressed air in accordance with instructions in a working program, and/or in response to a detected negative pressure sensed by means of a pressure sensor that communicates with the air suction duct. In a maximally decentralized embodiment, each suction cup has one or more dedicated ejectors, valve units and control members, and therefore only compressed air and electrical supply need to be led up to the individual suction cup.
From WO 2006/039939 A1, there is known an ejector device of the type generally described above, which is provided with an energy-storing member for temporary electrical supply of a control and/or a valve unit upon power failure. The energy-storing member may be in the form of a capacitor, a battery, an accumulator or a magnetic coil. The energy-storing member guarantees that negative pressure is maintained in the air suction duct during a temporary power failure, but does not avoid the need of electric connection of the ejector and thereby does not result in a simplified installation in comparison with prior art.